Marks mixes boxing techniques into his training sessions for people with Parkinson’s disease, the neurological brain disorder affecting about 1.5 million people in the United States. It’s a concept that has been catching on in recent years, with former boxers and gym trainers throughout the country launching programs to help Parkinson’s patients looking to benefit from the pow-pow-pow, high-cardio regimen.

“Exercise at high levels can start to stimulate and produce low levels of dopamine, which is lost with Parkinson’s,” Marks says.

“I won’t hit them, but they might hit me,” adds Marks, jokingly, as he continued blocking jabs during the recent morning session with Defreitas.

Parkinson’s patients, typically diagnosed at age 60 or 70, take various medications to slow the march of the disease, which occurs when brain cells that produce dopamine begin to die off. People then begin to lose coordination, balance and muscle control, leading to rigid muscles and tremors that can cause loss of independence and, sometimes, depression.

For Marks, the sparring sessions began as a personal journey. His late father, Harold Marks, struggled with Parkinson’s in his 60s.

“One day I went to see my dad and he was down, feeling sorry for himself. I went to my car and grabbed my (boxing) gear pads and a light bulb went off in my head. I told him, ‘Hit the gloves. Come on.’ I started insulting him,” Marks recalls. “He got angry, stepped forward and started hitting me and running around the room. He was reacting. His adrenaline shot up.”

At the time, Marks thought his father’s physical therapy, which involved stacking multi-colored cones, wasn’t working. So he began looking into how boxing might help.

Dr. Carlos Singer, a Broward County, Fla., neurologist, says any regular exercise, whether high or low impact, can help increase levels of substance in the bloodstream that has to do with nerve cell growth.

Although he hadn’t heard of boxing therapy, he notes that exercise – whether it’s walking, dancing or shadow boxing – can improve a Parkinson’s patient’s gait, stamina, energy level and overall quality of life.

“It’s a dose of exercise,” says Singer, director of the University of Miami Miller School of Medicine’s Center for Parkinson’s Disease and Movement Disorder Center. “There are a number of studies that are showing that exercise improves functioning with Parkinson’s disease. We advise our patients to get involved with regular exercise.”

Of course, one wouldn’t want to be punched in the head like professional boxers, who have been known to suffer from Parkinson’s after years of the sport.

“If you can punch a bag, shadow box or spar, then it should be OK,” Singer adds.

Marks trains one-on-one with his clients in a small warehouse-type setting inside an office park. His demeanor: friendly but tough.

Students say the sessions help with flexibility, improve hand-eye coordination and strength building and lift their self-confidence. The workouts also help patients release their frustrations and anger associated with the condition, which doesn’t have a cure and can make simple tasks such as buttoning a shirt or picking up a glass difficult.

Lisa McFarland, of Pembroke Pines, Fla., has been training with Marks for four years and says the intense workout helps her manage her tremors better.

When she’s boxing, “you’re having to multi-task in your head with everything that is going on. It’s a little harder than running on a treadmill or doing situps,” says McFarland, 53, who was diagnosed 11 years ago. “There are a lot of things that have to go on at the same time.

“With Craig, he will say, ‘Give me a left-right-left.’ And if you don’t duck, he is swinging. You are still trying to think of what the third punch is.”

To warm up, Marks has patients run up and down stairs or jog outside. They also use their abs to balance themselves as they move small platforms or risers from side to side.

Defreitas, of Davie, Fla., was diagnosed with Parkinson’s six years ago at age 42. “At first I didn’t think I had Parkinson’s because of my age,” he says. “When I would read the newspaper, my left arm would shake.”

The pressure-cleaning business owner says the classes help loosen up his stiff muscles. The disease mostly affects his left side, causing him to drag his leg or walk slowly. He speaks in a low voice, another symptom of the condition.

After an hour of punching and kicking a bag, a sweaty Defreitas, who had arrived this morning moving cautiously, seems invigorated.

“I feel great,” he says toward the end of his session, ready for another round.